The present invention relates to portable sign assemblies and, more particularly, relates to a portable sign assembly having a frangible post to readily breakaway when impacted by an errant vehicle.
Federal, state, and local governments require that signposts and other structures associated with road construction be of a type designed to ensure the safety of motorists in the event of a collision with the signposts or other structures. Specifically, the Federal Highway Administration (FHWA) sets standards and oversees the design and construction of traffic signposts on federal highways. Signposts must also conform to standards set by the National Cooperative Highway Research Program (NCHRP) and the American Association of State Highway Transportation Officials (AASHTO).
According to NCHRP Report 350 (hereinafter xe2x80x9cNCHRP-350xe2x80x9d), a goal of a highway safety feature, such as a sign, is to provide a forgiving roadway and roadside for an errant motorist. This safety goal is met when the highway feature readily breaks away, fractures, or yields without causing serious injuries to the occupant of the vehicle or to other motorists, pedestrians, or work zone personnel. Moreover, it is a goal that no portion of the sign assembly should enter the passenger compartment of the vehicle.
According to NCHRP-350, Tests 70 and 71 relate to the testing of Work Zone Traffic Control Devices. According to these tests, the work zone traffic control device is tested at various impact speedsxe2x80x94a low-speed test at approximately 35 km/h and a high-speed test at approximately 100 km/h. The low-speed test is generally intended to evaluate the breakaway, fracture, or yielding mechanism of the device whereas the high-speed test is intended to evaluate vehicular stability and test article trajectory. Occupant risk is of concern in both tests.
When applying these tests and standards to existing portable highway signs, it has been found that portable highway signs having generally rigid, metallic sign displays may not be thrown clear when impacted by an errant vehicle. That is, upon impact, conventional portable highway signs may be forced against the hood and/or roof of the vehicle rather than being thrown clear of the vehicle. This effect is particularly noticeable with portable highway signs having rigid, metallic sign displays. On the other hand, state departments of transportation and local highway construction companies own substantial numbers of rigid, metallic, and/or wood sign displays that are used in conjunction with fixed signs and portable signs. Many of these rigid, metallic, and wood signs are unique to various applications, such as merging, caution, and the like. As such, these rigid, metallic, and wood signs represent a significant investment made by these states and local highway construction companies over the course of many years. Current replacement of these rigid, metallic, and wood signs inventories with comparable flexible rollup sign displays is not financially feasible for many of these states and companies due to the cost of such flexible sign displays. Accordingly, there exists a need to provide a portable, breakaway highway sign and/or retrofit for use with existing rigid, metallic, and wood sign displays that complies with NCHRP-350.
As determined by these tests and usage experience, breakaway signposts have proven to be highly effective in reducing vehicle damage and occupant injury resulting from collision therewith. A variety of breakaway signpost constructions intended to meet safety requirements for highway installations have been used in the prior art for installation of permanent highway traffic signs.
Conventional breakaway connections are typically provided between a relatively short section of post (base post or ground post) that is permanently driven into the ground, and a longer section of post (support post) that extends upwardly above the ground from the base post and supports the sign. When the motor vehicle collides with the signpost or posts, the section of the signpost above the ground is typically sheared off (through the use of shearing bolts) or hinged over to allow the motor vehicle to continue on its path with minimum damage to the vehicle and without injury to its occupants.
One particular type of signpost that has been used extensively in the prior art comprises a pair of square shaped members that are coupled together through a collar member. The collar member includes a pair of holes which tend to weaken an area between the pair of square shaped members to provide a breakaway feature as shown in U.S. Pat. No. 5,782,040.
Another particular signpost that has been used extensively in the prior art comprises a generally circular post member having a flanged lower end that is bolted to a permanent support structure, such as a concrete base. The bolts used to fasten the circular upper support post to the base structure are typically sized to permit the shearing of these bolts upon contact from an errant vehicle as shown in U.S. Pat. No. 3,951,556.
However, both of the above prior art breakaway connections, which use various sections bolted together, suffer from similar disadvantages. For instance, these breakaway connections require multiple parts to be assembled. This leads to potential difficulties in assembly depending on the size and weight of the components. That is, in order to fasten an upper support post to the lower base structure using a plurality of fasteners, that person is required to extend multiple fasteners through the lower post section, hold the upper post section in proper orientation while positioning it over the fasteners without dislodging the fasteners and then secure the fasteners by placing and tightening washers and nuts on them, for example, all while holding the upper post section in proper upright alignment. Many times heavy equipment, such as a hoist, is used to support the upper section while the fasteners are installed and tightened to make the final connection.
It is important that signposts, irrespective of size, be capable of withstanding ambient wind loads normally encountered by highway sign installations. Experience has shown that signs supported by a single support post, especially, tend to flutter when subjected to wind loads and this fluttering action imposes torsion on the post and fasteners holding the post sections together. This torsional loading of conventional signposts and fastener systems leads to frequent failure of the fasteners and/or post. Similarly, conventional portable sign assemblies must withstand these ambient wind loads, yet must also withstand the rigors of being transported and handled.
Accordingly, there exists a need in the relevant art to provide a breakaway highway signpost that is capable of being manufactured and assembled in a simple and cost effective manner. Furthermore, there exists a need in the relevant art to provide a highway signpost that provides a breakaway feature to minimize damage and/or intrusion into the passenger compartment of an errant vehicle. Still further, there exists a need in the relevant art to provide a highway sign assembly that is portable between construction sites. Additionally, there exists a need in the relevant art to provide a breakaway signpost that can enable the current inventory of conventional rigid signs to be used in applications that meet the federal safety standards. Lastly, there exists a need in the relevant art to provide a highway signpost and assembly that overcomes the disadvantages of the prior art.
In accordance with the broad teachings of this invention, a portable signpost assembly having an advantageous construction is provided. The portable signpost assembly includes a portable base structure and a frangible support post coupled to the portable base structure. The frangible support post includes a plurality of corners when viewed in cross section, wherein at least one of the corners includes a notch formed therein that promotes localized fracturing of the frangible support post upon contact from a motor vehicle. This enables the frangible support post to be broken away from the portable base structure upon impact from an errant vehicle to permit the sign and support post to travel over the vehicle without entering the passenger compartment.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only.